German Patent DE 30 06 379 discloses a defect inspection system for comparative inspection of a standard specimen and a test item. The test item and the standard specimen are on a common support, and both the standard specimen and the test item are imaged via optical means and combined so that a comparison is possible.
German Unexamined Application DE 41 03 457 describes a comparison microscope for viewing two similar specimens through two objectives, having a device which is configured for combining the two images for comparative viewing. Each of the two objectives is part of an individual microscope, a video mixing apparatus, to which the video signals of two video cameras acquiring the images from the microscopes are conveyed, being provided as the device for combining the two images. Synchronous displacement of the microscope stages has not been acknowledged.
U.S. Pat. No. 4,403,839 describes a comparison optical device that is embodied for simultaneous observation of two specimens. A bridge encompasses the optical means for combining the beam paths that are generated by the microscope or macroscope. Illuminating light is introduced into the system by means of the photo tube. The document does not mention how the individual specimens must be arranged on one or more stages.
These macroscopes or microscopes described above are used in corresponding systems, which are embodied as comparison microscopes or comparison macroscopes, for performing forensic comparative examinations. In a very well-known embodiment, two individual microscopes or individual macroscopes, connected to one another by a bridge, are used. The bridge contains an apparatus for combining the two individual images generated by the individual microscopes or macroscopes. Through a common tube arranged on the bridge, the operator of the comparison microscope or macroscope can view in superimposed fashion the images of specimens arranged on two different stages. Appropriate blocking of portions of the two samples corresponding to one another yields a composite image which makes possible a direct comparison, for example, of one sample half to the other sample half.
In forensic investigations, crime-solving often requires that an image of a first sample be compared to the image of a second sample in order to obtain more detailed information about the circumstances of a crime.
The specimens compared to one another are, for example, the impressions produced on cartridge cases by the firing pin of a weapon, in order to determine whether the same firearm was used in two or more crimes.
A further known application of optical comparison investigations consists in checking the authenticity of documents, especially banknotes, in order to determine whether they are counterfeit.
Lastly, crime-solving often requires comparing, for example, clothing fibers found at the crime scene to fibers of known articles of clothing, in order to obtain information about how a perpetrator was dressed at the time of a crime.